Cr-Doped CeO2 Nanorods for CO Oxidation: Insights into Promotional Effect of Cr on Structure and Catalytic Performance

• Published in: Catalysis letters 2020-04, Vol.150 (4), p.948-962
• Main Authors: Venkataswamy, Perala, Damma, Devaiah, Jampaiah, Deshetti, Mukherjee, Deboshree, Vithal, Muga, Reddy, Benjaram M.
• Format: Article
• Language: English
• Subjects: Catalysis; Catalysts; Cerium oxides; Chemistry; Chemistry and Materials Science; Chromium oxides; Industrial Chemistry/Chemical Engineering; Lattice vacancies; Low temperature; Morphology; Nanorods; Noble metals; Optical properties; Organometallic Chemistry; Oxidation; Oxygen; Performance evaluation; Physical Chemistry; Solid solutions; Surface area; Synthesis; X ray photoelectron spectroscopy
• ISSN: 1011-372X; 1572-879X
• DOI: 10.1007/s10562-019-03014-z

Development of non-noble metal catalysts for oxidation of CO is an important subject for reducing the automotive emissions. Recently, shape-controlled synthesis of CeO 2 has increasingly attracted the attention of researchers due to its size- and morphology-dependent unique properties. Following this line of thinking, herein, we successfully report the synthesis of Cr-doped CeO 2 (Ce 1−x Cr x O 2−δ ; X = 0.05, 0.1, and 0.15) nanorods with various Cr contents by a facile hydrothermal method. Structural, surface, optical, and redox properties of the Cr-doped CeO 2 nanorods were investigated by various techniques, namely, ICP-OES, TEM-HRTEM, FE-SEM/EDX/EDS, XRD, BET, Raman, UV–vis DRS, PL, XPS, H 2 -TPR, and O 2 -TPD. The catalytic performance was evaluated for CO oxidation. For comparison, the efficiency of Cr 2 O 3 was also studied for CO oxidation under identical conditions. As revealed by various characterization results, the chromium ions were doped into the ceria lattice (formation of Ce–O–Cr solid solution), which enhanced the intrinsic properties such as oxygen vacancy concentration and surface area. It was found that the Cr-doped CeO 2 nanorods show superior CO oxidation activity than the pristine counterparts (CeO 2 nanorods and Cr 2 O 3 ). The highest CO oxidation efficiency was achieved with the light-off temperature of T 50  = 261 °C, when the Cr doping amount was 10% (Ce 0.9 Cr 0.1 O 2−δ ). A high specific surface area, more number of surface oxygen vacancies, a high concentration of Ce 3+ , and enhanced oxygen reducibility of Ce 0.9 Cr 0.1 O 2−δ nanorods were found to be responsible for its superior catalytic performance. Further, the Ce 0.9 Cr 0.1 O 2−δ nanorods exhibited a steady CO conversion over a period of 55 h investigated. The obtained results are expected to have a significant impact on the use of non-noble metal based Cr-doped CeO 2 nanorods in environmental applications. Graphic Abstract The Cr-doped CeO 2 nanorods with Ce 0.9 Cr 0.1 O 2−δ composition showed enhanced CO oxidation performance at a lower temperature (~ 261 °C) than that of pristine CeO 2 nanorods (338 °C) and Cr 2 O 3 (361 °C) catalyst. This behaviour is a result of enhancement of oxygen vacancies, surface Ce 3+ species, low-temperature reducibility, and high surface area.